1. Field of the Invention
The present invention relates to an ultrasonic diagnostic apparatus for providing an image of a cavity portion of an organ as a three-dimensional image.
2. Description of Related Art
Ultrasonic diagnostic apparatuses which transmit and receive ultrasound with respect to a living body and which then provide a three-dimensional image of inside the living body based on a received ultrasonic signal have been known. In general, the three-dimensional image thus obtained is a solid representation of information concerning a brightness value of each voxel. In this case, however, a cavity portion inside an organ cannot be observed. When observing a heart, for example, a cardiac muscle portion is brightly displayed because ultrasound is reflected by the cardiac muscle of the heart, and no information can be obtained regarding a cavity portion inside the organ, such as the characteristics or behavior of a ventricle. Therefore, in order to observe a cavity portion, a processing is conventionally performed in which a cutting plane is specified and an image of the cavity portion is displayed while information concerning regions in front of the plane is eliminated, for example.
Further, in diagnosis regarding the heart, there is a demand for obtaining a stroke volume of the heart. Conventionally, an approximate stroke volume has been obtained based on a tomogram of the heart or the like. For example, the length of a predetermined portion of the left ventricle is measured and the stroke volume is obtained based on sequential change of this length over time, or, in another example, the cross sectional area of the left ventricle at a certain cutting section is obtained and the stroke volume is calculated based on sequential change in this cross sectional area with time.
When a cavity portion inside an organ is observed, necessary information is often provided by the state of the inner wall surface of the cavity. Accordingly, when a cavity is observed in such a manner that a cutting plane is specified and information concerning regions in front of the cutting plane is eliminated, as conventionally performed, it is not possible to observe the regions of the cavity which have been eliminated.
Further, according to the conventional method, a volume of a cavity portion being observed is only an assumed value based on the length of a predetermined part and the area of a predetermined section. Therefore, an accurate volume cannot be obtained.